1. Field of the Invention
This invention relates to cephalosporin analogs. In particular it relates to cephalosporin analogs having a dihydropyridine ring.
2. Description of Prior Art
Cephalosporins are valuable antibiotics. However, microorganisms, in time, develop strains which are immune to existing antibiotics. Accordingly, new antibiotics will be required with high antibacterial activity.
Cephalosporin analogs have previously been developed where a carbon atom is substituted for the sulfur atom in the dihydrothiazine ring of the cephalosporanic acid ring system. Such compounds are known as carbacephems. In the Journal of the American Chemical Society, 96, 7584 (1974) and J. Med. Chem., 20, 551 (1977), carbacephems having substituted methylene groups at the C-3 position have been proposed, such as (.+-.)-1-carbacephalothin [(.+-.)-7.beta.-(2-thienyl)acetamido-1-methylenedethiacephalosporanic acid].
In commonly assigned, copending application Ser. Nos. 023,645 and 023,646, carbacephems having a hydrogen atom at the C-3 position have been disclosed.
It has now been discovered that novel carbacephems can be prepared having a dihydropyridine ring in place of the tetrahydropyridine ring of the carbacephems referred to in the J.A.C.S. article, Vol. 96, 7584 (1974).